The present invention relates to a press brake for bending and otherwise forming sheet material. More specifically, the invention relates to a pressure/spring actuated clamping system to secure a punch and die set to a press brake.
Press brakes are industrial devices used to bend or otherwise form sheeted material such as sheet metal. A press brake includes a bed and a ram which is disposed above, and vertically movable over, the bed. Both the ram and bed extend across the entire front portion of the press brake. Clamps for securing a punch and a die (i.e. the tool set) are provided respectively, on both the ram and the bed. The punch extends downwardly from the ram and the die extends upwardly from the bed to matingly receive the punch. Bending or forming of the sheet material or work piece is accomplished by forcefully lowering the ram and punch thereby sandwiching the work piece between the punch and die.
In a typical press brake operation, sheeted material is placed between the punch and die and aligned according to the plans or requirements of the particular job. With the material properly oriented, the ram is moved vertically downward thereby moving the punch toward the die. As the punch is lowered, it contacts the sheeted material and, with adequate force exerted by the ram, the sheeted material is bent or otherwise formed to conform to the shape defined by the mating surfaces of the punch and die. The bends in the sheeted material are unique to the particular tool set combination employed for each job.
Conventionally, the tool set is clamped on the ram and bed by tightening a series of bolts or set screws spaced at approximately twelve inch intervals. A long recognized difficulty with conventional press brakes is the lengthy set-up time required when one tool set is substituted for another. Large press brakes have rams and beds which often exceed 10 to 20 feet in length, consequently, more than a dozen bolts or screws must be loosened and retightened each time the tool set is changed. The problem of set-up time is particularly acute where the tool set must be replaced frequently, that is, where numerous jobs of small lot size are contemplated. Use of large tools, with their correspondingly high number of securement bolts, further aggravate the set-up time problem.
In order to solve this problem, a pressure/spring actutated failsafe clamping system is utilized to eliminate the need for loosening and retightening numerous bolts each time the tool set is changed. The system includes separate bed and ram clamp assemblies; each assembly comprising a fixed and a slidable clamping member. The bed clamp assembly, which is of an interlocking, L-shaped configuration to alleviate misalignment of the tool die upon clamping, is positioned on the bed of a conventional press brake.
It should be noted that pressure actuated clamp mechanisms have been commercially available for some time. Such mechanisms, however, exhibit certain shortcomings for which the present invention was developed to overcome. Specifically, conventional systems require positive pressure to keep the clamp jaws securely closed. In systems of this type, a sudden loss of pressure will cause the clamp jaws to open, potentially releasing the object held therebetween. Such a pressure loss can occur by the rupture or accidental severing of a hydraulic line or upon the interruption of electric service at the site. As many punches do not incorporate additional safety features to assure retention of the punch upon loss of clamping action by the ram clamp, the loss of pressure could result in the release of the punch weighing hundreds of pounds.
The present invention avoids the loss of pressure problem of conventional systems. Specifically, the present invention operates in a failsafe manner by requiring positive pressure to open the clamp jaws. Unlike conventional systems, a sudden loss of pressure will close the clamp jaws thereby avoiding the potentially dangerous situation existing in prior art systems.
Therefore, it is an object of this invention to provide a simple, yet effective, solution to the problems raised by conventional press brake clamps.
It is another object of this invention to reduce the time required to change a tool set on a press brake by eliminating the need to loosen and retighten a series of bolts or set screws every time a tool set is changed.
It is still another object of this invention to provide a pressure/spring actuated clamping system for use on a press brake.
These and other objects and advantages of this invention will become apparent from the remaining portions of this specification.